Spiced mackerel on toast with beetroot salsa

Name: Spiced mackerel on toast with beetroot salsa
Ingredients: 250g pack beetroot (not in vinegar), diced; 1 eating apple, cut into wedges then thinly sliced; 1 small red onion, finely sliced; juice ½ lemon; 1 tbsp olive oil, plus extra for drizzling; 1 tsp cumin seed; small bunch coriander, leaves roughly chopped; 4 mackerel fillets, halved widthways; 1 tsp curry powder; 4 slices sourdough bread or ciabatta